1. Technical Field
The present invention relates to a biological information detection apparatus and the like.
2. Related Art
A biological information detection apparatus which detects biological information, such as a pulse wave of a human, is hitherto known. JP-A-2011-139725 and JP-A-2009-201919 disclose a pulsimeter of the related art which is an example of the biological information detection apparatus. The pulsimeter is put on, for example, an arm, a wrist, a finger, or the like, and detects pulsation resulting from heartbeat of a human body to measure a pulse rate.
The pulsimeter disclosed in JP-A-2011-139725 and JP-A-2009-201919 is a photoelectric pulsimeter, and a detection unit (pulse wave sensor) of the pulsimeter has a light emitting unit which emits light toward a subject (a region to be detected), and a light receiving unit which receives light (light having biological information) from the subject. In this pulsimeter, change in blood flow is detected as change in the amount of received light, thereby detecting a pulse wave. JP-A-2011-139725 discloses a pulsimeter which is put on a wrist, and JP-A-2009-201919 discloses a pulsimeter which is put on a finger.
In JP-A-2011-139725 and JP-A-2009-201919, a light transmitting member which transmits light from the light emitting unit or light from the subject is provided, and the light transmitting member has a contact surface with the subject (the skin of the wrist or the finger). Then, if a convex portion is provided on the contact surface of the light transmitting member, a pressing force is easily applied when coming into contact with the skin of the subject.
However, as a side effect, there is the effect of change in pressing force caused by shaking of the instrument of the biological information detection apparatus by body motion, motion (for example, clasp and unclasp operation) of the hand of a user on which the biological information detection apparatus is put. When change in pressing force is large, this means that a body motion noise component which is superimposed on a detection signal of the biological information is large.
For example, if the convex portion of the light transmitting member formed of a hard material comes into contact with a soft surface of a living body, such as skin, a flat portion around the convex portion and the surface of the living body are in a non-contact state or a weak contact state, or the like, and the contact state dynamically changes. If dynamic change in the contact state occurs, light intensity is likely to be optically generated, and if light enters the light receiving unit, light becomes noise having no correlation with a pulse component, and quality of a detection signal of the biological information is deteriorated.
In this biological information detection apparatus, it is desirable to make the amount of received light, which passes through the light transmitting member from the subject and enters the light receiving unit, as large as possible. It is also desirable to make the amount of light, which passes through the light transmitting member from the light emitting unit and is emitted toward the subject, as large as possible.
When the light transmitting member having the convex portion or the detection unit is embedded in the biological information detection apparatus, improvement of waterproof performance, ease of assembling, or the like becomes an important element.